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Sensors developed for consumer applications are being picked up by industrial users – and for robotics in particular

Sensors have always been an important part of the industrial environment, measuring such variables as temperature, pressure and load. But the operative word was ‘industrial’, implying devices that were relatively large and relatively unsophisticated.

The appearance in the 1980s of MEMS technology changed all that. All of a sudden, sensors became much smaller and capable of being integrated into a range of new applications. And, when combined with electronics, such sensors became intelligent.

The miniaturisation of sensors has continued to the point where smartphones now integrate devices with the ability to measure such things as angular rotation and gravity – even air quality.

One of the pioneers of the MEMS sensor industry is Bosch Sensortec, which emerged from Bosch’s automotive activity and is now an independent company. “But we have a deep connection to Bosch,” said Wolfgang Schmitt-Hahn, director of strategic marketing, “and share its processes.”

He admitted that a large proportion of Bosch Sensortec’s output was supplied to the smartphone sector. “We’re supplying accelerometers for use in low end handsets,” he remarked, “but also sensors for wearables such as fitness trackers. Now, we’re developing a strong position in VR.”

So far, Bosch Sensortec has made more than 9billion sensors, with 75% of that output – such as gyroscopes and magnetic sensors – supplied to the consumer electronics sector.

“Today,” Schmitt-Hahn continued, “developing sensors is also about packaging, adding intelligence and writing software and algorithms.”
While many of the sensors developed for use in smartphones may not be appropriate for industrial use, some are and system developers are taking advantage.

“While the consumer electronics sector is driven by the cost cycle, industrial users want these products to be available for more than five years,” Schmitt-Hahn pointed out, “and cost is not as important to them.” But Bosch Sensortec isn’t developing devices for use in hard industrial environments; instead, it’s addressing low impact industrial applications where sensors developed for consumer products can be used. “In that way,” he continued, “industrial customers can benefit.”

One of the issues is that, while smartphones, for example, have well defined sensor requirements, industry has a wide range of potential use cases. “Even so, we can look at how an accelerometer developed for a smartphone could be used to measure vibration on a machine,” he said.

Ralf Schellin, director of product management, said this could bring problems, particularly when sensors were being retrofitted. “We have seen our sensors added to air conditioning systems, but they need to be connected properly. If you have a pressure sensor, that needs to be connected to a pressure tube in the air conditioning system and that can mean connecting two different materials. Besides the electronics, there are mechanical elements, which can make things more difficult.”

At the 2018 Consumer Electronics Show, Bosch Sensortec unveiled the BMI088, an inertial measurement unit (IMU) designed for drone and robotics applications. The device integrates an extremely stable gyroscope, with a low noise, low drift output.

“Challenging applications, such as drones and robotics, demand extremely stable and high performance IMUs,” said Dr Stefan Finkbeiner, Bosch Sensortec’s CEO.

The BMI088 consists of a triaxial 16bit acceleration sensor and a triaxial 16bit gyroscope integrated into a package measuring 3 x 4.5 x 0.95mm. With a bias stability said to be less than 2°/hr and a temperature offset coefficient of 0.2mg/K, the accelerometer can measure ±24g.

Schellin said that, while the BMI088 had been demonstrated on a drone at CES, the device was robust enough for industrial use. “The sensor was on a PCB in a robust housing, designed to resist EMI and capable of operating in temperatures ranging from -40 to 85°C. If we have better domain knowledge, then we can better tailor sensors to customer requirements.”

Industrial users can also take advantage of the power consumption benefits provided by sensors developed for consumer applications. Schmitt-Hahn pointed to the Internet of Things and Industry 4.0 applications. “If you think about retrofitting sensors in these applications, then it’s likely you would use a wireless device. You can certainly think about applications where you not only need sensors with low power consumption, but also a low power solution.”

While it may be beneficial to integrate a small sensor into an industrial application, such as robotics, it’s still important to be able to use the data generated in a sensible way. And that means software has become as important as the sensor itself.

“We can do this in a number of ways,” said Schmitt-Hahn. “There are some sensors where all we need to do is to supply the device with a library of drivers. But there are also more complex parts. For example, a motion sensor might feature an accelerometer, a gyroscope and a geometer; each with three axes.

“That creates nine axes and, to make that raw data useful, it requires us to develop the software because we know our sensors best.”

Data rate is also an important factor, particularly in the rapidly developing field of VR. “Software allows data to be aggregated from a number of inputs,” he added.

Making sense of data coming from a large number of inputs is pushing companies such as Bosch Sensortec to add intelligence within the package. “We do this either by integrating MCUs inside the package or including an MCU core,” Schmitt-Hahn noted. “This local intelligence is provided by MCU structures optimised for the process. It’s important to point out that this doesn’t waste space nor power.”

But there is a limit to how much software the company can develop for its sensors. “Whenever we can support an application, we do. But while we help customers solve application problems, we don’t have specific solutions for particular applications.

“When it comes to connecting sensor data into other algorithms – vibration measurement, for example – the expertise has to be provided by the customer. What we have to do is to build the bridge between the sensor and the customer’s system,” said Schmitt-Hahn.

"Developing sensors is also about packaging, adding intelligence and writing software and algorithms."
Wolfgang Schmitt-Hahn

Schellin reinforced this point. “The customer has the domain knowledge and creates the application layer. Our job is to create the bridges by adding an intermediate layer. Then, it depends on the application.

“In a step counting application, the output is the number of steps and the customer’s task is to represent that data. In more complex applications, the output could be Euler angles and that means the customer has to do more than simply develop an HMI.”

Process technology is playing an important role in creating smaller sensors which consume less power. “We’re using state of the art CMOS,” Schmitt-Hahn noted, “and we’re always trying to shrink devices as much as possible and to move to different process nodes. But we have to strike a balance between cost and power consumption. For example, there may be more power leakage on a smaller node.”

Most Bosch Sensortec products are provided as systems in package, with the MEMS and CMOS elements as separate dice. “The challenge is to decide how many dice should be put into one package,” Schmitt-Hahn concluded, “and how we put these things into a package without having problems with stress and bending.”

Nine axis sensor features Cortex-M0+ MCU

The BMF055 is a compact nine axis motion sensor that can be programmed for particular applications. With sophisticated motion sensing capabilities, the part is said to replace multiple discrete components.

The sensor, from Bosch Sensortec’s Application Specific Sensor Node family, integrates an accelerometer, a gyroscope, a magnetometer and a Cortex M0+ processor from Atmel’s SAMD20 family into a package measuring 5.2 x 3.8 x 1.1mm.

The device is said to be suited to the needs of customers developing advanced application specific sensor fusion algorithms, including robotics.

Author
Graham Pitcher

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